Quenching oils



Patented Feb. 18,1936

- UNITED STATES QUENCHING OILS George Chapelton Shepherd, Jr. Long Beach, 7 Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application January 9, 1933,. Serial-No. 650,863

3 Claims. (c 148-18) This invention relates to quenching oils for use in the metallurgical industries, to methods for their production, and to methods of quenching where these oils are employed.

The object of the invention is to furnish quenching oils which will afford greater cooling velocities throughout the critical and tempering stages than heretofore, and which at the same time will notdeteriorate materially under the severe service conditions to which said oils are subjected. In the past no quenching oiIof high cooling ve-.- locity has been known, and many of those avail.- able have been subject to great deterioration in use as has been indicated by aresultant thick ening and formation of sludge. This has been true particularly of those types including fish and animal oils.,

-I have discovered that, by employing mineral oils which have been so heat-treated as to be highly resistant to further change by heat, quenching may be efficiently accomplished and deterioration of the quenching oil will be almost entirely eliminated. Such oils are cracked-oils of sufficiently low viscosity and volatility as to be suitable for quenching purposes and to afford the desired high cooling velocities. Thus certain fractions suitable for these ends are obtained by the distillation of cracked residuums which have been produced by the well knowncracking processes for conversion of petroleum into lighter products, as inthe manufacture of motor fuels.

Other suitably heavy fractions of cracked disti1-.

lates also are'included. One important advan tage of these cracked oil's resides in their great ly as covering quenching oils comprising rela-, r tively non-volatile cracked fractions of low viscosity obtained from the cracking Of mineral oils. The invention particularly includes such fractions where obtained by distillation of cracked mineral oil residuums resulting from the various well knowncracking processes, as well as from residuums from other hydrocarbon cracking processes The invention includes further the meth-- -ods of manufacturing such quenching oils and methods for. quenching metals therewith. Considering the invention in greater detail; oils which possess the required non-deteriorating 'ticularly severe cracking operations, and in addicharacteristics include particularly those which are recoverable by distillation from residuums from the cracking of hydrocarbons particularly of mineral oils and mineral oil products as in the case of the manufacture of cracked gasoline. I These residuums consist largely of complex polymers which have been formed incidental to the cracking processes, and when these polymers are separated as suitable fractions, they are found to present the desired stable properties here 'con- 10 sidered essential to good quenching oils. In general, the more severe the cracking, the more useful will be the product. Where petroleum and petroleum fractions have been cracked either by liquid phase or vapor phase methods, the residuums or liquid bottoms resulting from the fractionation of the cracked products constitute suitable stocks from which the desired quenching oils may be obtained.

For example, such a stock is the heavy residuum resulting where a gas oil obtained from 9. California or other asphaltic crude, such as San Joaquin Valley crude, is cracked by-means of a recycling process at temperatures around 850 to 900 F. when producing cracked gasoline. This residuum results after removal of the lighter cracked products therefrom. Other residuums which will serve as suitable stocks are those re: covered from other cracking operations, partion to those from the cracking of petroleum liquids or vapors, residuums obtained from the cracking of natural gas orsimil arhydrocarbons will constitute satisfactory stocks.

Having obtained a crackedresiduum. of the character stated, the residuum itself is then distil1ed, as by means of steam distillation atatmospheric pressure to separate the oil into fractions of varying volatility. The first fractions, if they have the characteristics of kerosene or light gas oil, will in themselves be too volatile and will therefore bediscarded but the succeeding heavier cuts which possess a sufliciently high flash point will be condensed and blended to produce an oil satisfactory for quenching purposes. Such an oil ordinarily should have a flash point not hiwer than about 300 F and for average purposes may for example have'a yiscosity of around 125 ,seconds Saybolt universal or less at 100 F. A suitable oil obtained from the San Joaquin Valley gas oil cracked by recycling as above' indicated, has a, rather wide,.boiling range'and'may have been obtained by distilling until the bottoms showed a melting point around 250 F; The

lightest fraction will ordinarily have been discarded however as above indicated, and the heavier fractions of proper flash point blended to yield the product. The desirable cracked oil fractions which I employ as the quenching oil are characterized by the property of having a greater density than that of uncracked' oils for the same viscosity range. A specific example of a'suitable product obtained from the mentioned gas oil is one having a viscosity of 115 seconds S'aybolt at 100 F. and an A. P. I. gravity of 7.9--at 60 F., and a flash point of 320 F. In general it may be said that satisfactory oils obtained as indicated probably should have viscosities which lie between about and 200 seconds Saybolt universal at F. and might have flash points as low as 250 F. in some instances. The oil fractions obtained are for the most part within the tion the quenching procedure, which consists in quenching the heated metal in the oil until properly cooled, results in a more rapid cooling, and as previously indicated results in elimination of substantially all thickening and formation of sludge and other deterioration heretofore commonly encountered in the use of quenching oils.

It is to be understood however that both lighter and heavier fractions may be employed, especial 1y for certain uses, so long as the volatility of the products does not exceed that of a safe flash point. Thus, any cracked fraction of sufficiently low volatility and sufficiently low viscosity may be segregated from the overhead or vaporized products obtained in any cracking process. For example, where manufacturing cracked motor fuels, the. overhead or vaporized, products are ordinarily recovered in the form of a lighter or gasoline fraction and a heavier fraction which is known as cycle stock and is returned to the cracking system. By in turn fractionating a quantity of this cycle stock in order to eliminate the lighter and more volatile portions, a heavier cut or liquid bottoms may be taken which will constitute a satisfactory quenching oil possessing the desired high flash point and low viscosityx Again, the above described residuum which is formed when the gasoline and cycle stock cuts The cracked fractions above described as having suitably low viscosity and volatility may be used as quenching oils without further treatment,

or they may be refined by any of the methods customary in refining petroleum products. However the distilled fractions which have been blended to produce an oil suitable for use in quenching, should in general, be chemically treated to remove highly unsaturated and other easily oxidized bodies which would tend to produce sludge during use. The treatment which I have found to be satisfactory, consists in subjecting the oil to the action of sulfuric acid of 98% strength at 100 to F. in the proportion of 25 pounds of acid per barrel of oil. After separating the sludge, the oil is neutralized with a solution of alkali, such as sodium hydroxide, and then water washed. The resulting treated oil may then be blown bright with air at a temperature of to F. and/or may be contacted with decolorizing clay to improve the color. While 98% acid is generally preferable, acids of lower strength as well as fuming acid may be employed.

The above described oils, whether refined or unrefined, present the desired characteristics of high flash point and such fluidity as to circulate freely for rapid cooling when in use. They may be used either alone or as the important com ponents of compounded quenching oils. For example small quantities of animal or vegetable oils may be added as is well understood by those skilled in the art; in a specific instance 15%, or more or less, of fish oil may be added, and other constituents as found advantageous or desirable may be included in the preparation of any particular compound for any special purpose.

It is to be understood that the specific disclo-.

sures hereof are not to be taken as limiting but merely as illustrative of the generic invention which relates to the use of any stable cracked product as a quenching oil.

I claim:

1. A method of quenching metals which comprises immersing the heated metal in a heavy cracked hydrocarbon oil fraction, said oil being characterized by having a flash point of 250 F. or higher and a viscosity of between 75 to 200 seconds, Saybolt universal at 100 F.

2. A metal quenching oil comprising a heavy cracked mineral oil fraction having a flash point of 250 F. or higher and a viscosity of 75 to 200 seconds, Saybolt universal at 100 F.

3. A method of quenching metals which comprises immersing the heated metal in a cracked hydrocarbon quenching oil'produced by cracking a mineral oil to yield cracked residuum, distilling said residuum and recovering said quenching oil as a heavy condensate characterized by a viscosity of between '15 to 200 seconds Saybolt universal at 100 F.

GEO RGE CHAPELTQN SHEPHERD, Jli. 

